1. Field of the Invention
The present invention generally relates to a light emitting diode module (LED module), and more particularly, to a driving module for driving an LED.
2. Description of Related Art
Due to low power consumption and high luminance, LEDs have been effectively applied in various applications, for example, illumination light, electronic bulletin board and traffic light. In particular, in display field, LEDs have excellent color performance within the gamut set out by National Television Standard Committee (NTSC); therefore, LEDs are gradually substituting a cold cathode fluorescent lamps (CCFL) employed by a backlight module of a display panel and the CCFL is a dominated light source used in a backlight module before.
However, the LEDs served as the light source of a backlight module of a display panel confront two stubborn problems. One of the problems is how to make a plurality of light emitting diode strings (LED strings) in a backlight module produce uniform luminance so as to have better display effect with a display panel. The luminance produced by an LED string is controlled by the current flowing through the LED string. Once only a fixed voltage is used to drive different LED strings, the characteristic difference between individual LED strings would result in nonuniform luminance as a whole.
To solve the above-mentioned problem, many different conventional schemes were provided. One of the conventional schemes is to utilize a plurality of sets of voltage-to-current converters for individually adjusting luminance of each of the LED strings. Although the above-mentioned scheme is able to individually adjust luminance of each of the LED strings to effectively overcome the problem resulted by the characteristic difference between the LED strings, but the conventional scheme requires a numerous voltage-to-current converters, which is not economical solution. Moreover in the prior art, there is time-division-multiplexing (TDM) scheme, by which the luminance corresponding to different LED string is adjustable to achieve balance of luminance. The conventional TDM scheme requires a clock signal with a high frequency and a plurality of switching signals produced based on the clock signal for switching a plurality of switches. The frequent switching of the switches tends to produce inrush currents leading to serious electromagnetic interference (EMI).